Light source control for projector with multiple pulse-width modulated light sources
View Patent ↗A color projection display in which at least one color channel includes: a light source assembly including a multiplicity of pulse modulated light sources providing an aggregate light beam; a light modulation control subsystem; illumination optics to direct the aggregate light beam to an image modulation plane; and a spatial light modulator in the image modulation plane. The light modulation control subsystem senses an aggregate light intensity signal for the aggregate light beam and controls the pulse modulation parameters for the multiplicity of pulse-modulated light sources responsive to the sensed aggregate light intensity signal to reduce light intensity fluctuations in the aggregate light beam within the imaging time interval.
1. A color projection display, comprising:
a plurality of color channels, in which at least one color channel includes:
a light source assembly including a multiplicity of pulse modulated light sources providing an aggregate light beam;
a light modulation control subsystem to control pulse modulation parameters for the multiplicity of pulse-modulated light sources;
illumination optics to direct the aggregate light beam to an image modulation plane; and
a spatial light modulator in the image modulation plane having an array of addressable pixel elements, each of which is pulse width modulated during an imaging time interval to impart image data to the transiting aggregate light beam to provide image light;
an optical combiner to redirect image light from the plurality of color channels onto a common optical path; and
projection optics to receive the combined image light traversing the common optical path and to project the combined image light onto a display surface;
wherein the light modulation control subsystem senses an aggregate light intensity signal for the aggregate light beam and controls the pulse modulation parameters for the multiplicity of pulse-modulated light sources responsive to the sensed aggregate light intensity signal to reduce light intensity fluctuations in the aggregate light beam within the imaging time interval, and wherein the pulse modulation parameters include pulse phase delay parameters for the multiplicity of pulse-modulated light sources that are controlled such that pulse trains from the multiplicity of pulse-modulated light sources overlap in an asynchronous fashion, and are controlled to randomly distribute the phases.
2. The color projection display of claim 1 wherein the pulse modulation parameters further include a pulse duty cycle parameter, or a pulse frequency parameter.
3. The color projection display of claim 1 wherein the light modulation control subsystem further controls the pulse modulation parameters such that an average aggregate light intensity for the aggregate light beam is substantially equal to an aim aggregate light intensity level.
4. The color projection display of claim 1 wherein the sensed aggregate light intensity signal is analyzed to determine when the performance of one or more of the pulse-modulated light sources has degraded or is unstable, and in response pulse phase delay parameters for at least the other pulse-modulated light sources are modified to reduce light intensity fluctuations in the aggregate light beam introduced by the performance degradation or instability of the one or more pulse-modulated light sources.
5. The color projection display of claim 1 wherein the sensed aggregate light intensity signal is analyzed to estimate differences in light intensities between the multiplicity of pulse-modulated light sources, and in response pulse modulation parameters for one or more of the pulse-modulated light sources are modified.
6. The color projection display of claim 1 wherein the light modulation control subsystem controls the pulse modulation parameters for the multiplicity of pulse-modulated light sources in one color channel responsive to sensed aggregate light intensity signals for a plurality of color channels.
7. The color projection display of claim 1 wherein the light modulation control subsystem controls the pulse modulation parameters for the multiplicity of pulse-modulated light sources in one color channel responsive to a white point sensed in the combined image light.
8. The color projection display of claim 1 wherein the spatial light modulator is a digital micro-mirror array device having an array of micro-mirrors, each associated with an image pixel, and wherein the orientation of the micro-mirrors is adjusted in a pulse width fashion during an imaging time interval to impart the image data to the transiting aggregate light beam.
9. The color projection display of claim 1 wherein the spatial light modulator is a liquid crystal device, a grating light valve device, or a grating electro-mechanical system device.
10. The color projection display of claim 1 wherein the pulse-modulated light sources include pulse-modulated laser devices, pulse-modulated laser array devices, pulse-modulated LED devices, or combinations thereof.
11. The color projection display of claim 1 wherein the imaging time interval is a frame time or a sub-frame time.
12. The color projection display of claim 1 wherein a plurality of color channels include light modulation control subsystems.
13. The color projection display of claim 1 wherein the light modulation control subsystem further senses individual light intensity signals for each of the multiplicity of pulse-modulated light sources, and wherein the process of determining the pulse modulation parameters for the multiplicity of pulse-modulated light sources is also responsive to the individual light intensity signals.
14. The color projection display of claim 3 wherein the aim aggregate light intensity levels for each color channel are specified to achieve a desired system white point.
15. The color projection display of claim 6 wherein the pulse modulation parameters are controlled to produce desired system white point.
16. The color projection display of claim 8 wherein the pulse modulation parameters for the multiplicity of pulse-modulated light sources are controlled to reduce light intensity fluctuations in the aggregate light beam within a time interval corresponding to a pulse width of a micro-mirror pulse associated with a least-significant bit of the image data.
17. A color projection display, comprising:
a plurality of color channels, in which at least one color channel includes:
a light source assembly including a multiplicity of pulse modulated light sources providing an aggregate light beam;
a light modulation control subsystem to control pulse modulation parameters for the multiplicity of pulse-modulated light sources;
illumination optics to direct the aggregate light beam to an image modulation plane; and
a spatial light modulator in the image modulation plane having an array of addressable pixel elements, each of which is pulse width modulated during an imaging time interval to impart image data to the transiting aggregate light beam to provide image light;
an optical combiner to redirect image light from the plurality of color channels onto a common optical path; and
projection optics to receive the combined image light traversing the common optical path and to project the combined image light onto a display surface;
wherein the light modulation control subsystem senses a light intensity signal for at least one particular pulse modulated light source and controls the pulse modulation parameters for a plurality of pulse-modulated light sources responsive to the sensed light intensity signal to reduce light intensity fluctuations in the aggregate light beam within the imaging time interval, and wherein the pulse modulation parameters include pulse phase delay parameters for the multiplicity of pulse-modulated light sources that are controlled such that pulse trains from the multiplicity of pulse-modulated light sources overlap in an asynchronous fashion.
18. The color projection display of claim 17 wherein the sensed aggregate light intensity signal is analyzed to determine when the performance of at least one of the the particular pulse-modulated light sources has degraded or is unstable, and in response pulse phase delay parameters for at least the other pulse-modulated light sources are modified to reduce light intensity fluctuations in the aggregate light beam introduced by the performance degradation or instability.
19. A method for providing illumination light in a color channel of an color projection system, the color channel including a light source assembly having a multiplicity of pulse modulated light sources, comprising:
operating the multiplicity of pulse-modulated light sources to provide a multiplicity of pulse-modulated light beams;
combining the multiplicity of pulse-modulated light beams to provide an aggregate light beam;
sensing a light intensity signal for the aggregate light beam;
determining pulse modulation parameters for the multiplicity of pulse-modulated light sources responsive to the sensed light intensity signal to reduce light intensity fluctuations in the aggregate light beam, wherein the pulse modulation parameters include pulse phase delay parameters for the multiplicity of pulse-modulated light sources that are controlled such that pulse trains from the multiplicity of pulse-modulated light sources overlap in an asynchronous fashion; and
directing the aggregate light beam using illumination optics to provide illumination light onto a spatial light modulator.
20. An illumination system, comprising:
a light source assembly including a multiplicity of pulse modulated light sources providing an aggregate light beam;
a light modulation control subsystem to control pulse modulation parameters for the multiplicity of pulse-modulated light sources; and
illumination optics to direct the aggregate light beam to an illumination plane;
wherein the light modulation control subsystem senses an aggregate light intensity signal for the aggregate light beam and controls the pulse modulation parameters for the multiplicity of pulse-modulated light sources responsive to the sensed aggregate light intensity signal to reduce light intensity fluctuations in the aggregate light beam, wherein the pulse modulation parameters include pulse phase delay parameters for the multiplicity of pulse-modulated light sources that are controlled such that pulse trains from the multiplicity of pulse-modulated light sources overlap in an asynchronous fashion.
21. The illumination system of claim 20 wherein the pulse modulation parameters further include a pulse duty cycle parameter, or a pulse frequency parameter.
22. The illumination system of claim 20 wherein the sensed aggregate light intensity signal is analyzed to determine when the performance of one or more of the pulse-modulated light sources has degraded or is unstable, and in response pulse phase delay parameters for at least the other pulse-modulated light sources are modified to reduce light intensity fluctuations in the aggregate light beam introduced by the performance degradation or instability of the one or more pulse-modulated light sources
23. The illumination system of claim 20 wherein the sensed aggregate light intensity signal is analyzed to estimate differences in light intensities between the multiplicity of pulse-modulated light sources, and in response pulse modulation parameters for one or more of the pulse-modulated light sources are modified.
24. The illumination system of claim 20 wherein the light modulation control subsystem further senses individual light intensity signals for each of the multiplicity of pulse-modulated light sources, and wherein the process of determining the pulse modulation parameters for the multiplicity of pulse-modulated light sources is also responsive to the individual light intensity signals.
25. The illumination system of claim 20 wherein the pulse modulation parameters for the multiplicity of pulse-modulated light sources are controlled such that the asynchronous pulse trains are randomly distributed or are substantially uniformly distributed.